ترغب بنشر مسار تعليمي؟ اضغط هنا

Testing the Standard Model under the weight of heavy flavors

435   0   0.0 ( 0 )
 نشر من قبل Chris Bouchard
 تاريخ النشر 2015
  مجال البحث
والبحث باللغة English
 تأليف C.M. Bouchard




اسأل ChatGPT حول البحث

I review recently completed (since Lattice 2013) and ongoing lattice calculations in charm and bottom flavor physics. A comparison of the precision of lattice and experiment is made using both current experimental results and projected experimental precision in 2020. The combination of experiment and theory reveals several tensions between nature and the Standard Model. These tensions are reviewed in light of recent lattice results.



قيم البحث

اقرأ أيضاً

110 - Marco Bomben 2012
The BaBar experiment recorded 471 x 10^6 BBbar pairs at the Y(4S) resonance (corresponding to an integrated luminosity of 429 fb^-1). We present here a selection of recent results from the BaBar collaboration: search for lepton-number violation in th e decay B^+ -> h^- l^+ l^+, search for lepton-flavor violation in B^+/- -> h^+/- tau l and CP-violation in tau^- -> pi^- KS (>= 0 pi^0) nu_tau.
We calculate the form factors for the semileptonic decays $B_sto Kell u$ and $Bto Kellell$ with lattice QCD. We work at several lattice spacings and a range of light quark masses, using the MILC 2+1-flavor asqtad ensembles. We use the Fermilab method for the $b$ quark. We obtain chiral-continuum extrapolations for $E_K$ up to $sim1.2$ GeV and then extend to the entire kinematic range with the model-independent $z$ expansion.
We present a lattice QCD calculation of the $Delta I=1/2$, $Ktopipi$ decay amplitude $A_0$ and $varepsilon$, the measure of direct CP-violation in $Ktopipi$ decay, improving our 2015 calculation of these quantities. Both calculations were performed w ith physical kinematics on a $32^3times 64$ lattice with an inverse lattice spacing of $a^{-1}=1.3784(68)$ GeV. However, the current calculation includes nearly four times the statistics and numerous technical improvements allowing us to more reliably isolate the $pipi$ ground-state and more accurately relate the lattice operators to those defined in the Standard Model. We find ${rm Re}(A_0)=2.99(0.32)(0.59)times 10^{-7}$ GeV and ${rm Im}(A_0)=-6.98(0.62)(1.44)times 10^{-11}$ GeV, where the errors are statistical and systematic, respectively. The former agrees well with the experimental result ${rm Re}(A_0)=3.3201(18)times 10^{-7}$ GeV. These results for $A_0$ can be combined with our earlier lattice calculation of $A_2$ to obtain ${rm Re}(varepsilon/varepsilon)=21.7(2.6)(6.2)(5.0) times 10^{-4}$, where the third error represents omitted isospin breaking effects, and Re$(A_0)$/Re$(A_2) = 19.9(2.3)(4.4)$. The first agrees well with the experimental result of ${rm Re}(varepsilon/varepsilon)=16.6(2.3)times 10^{-4}$. A comparison of the second with the observed ratio Re$(A_0)/$Re$(A_2) = 22.45(6)$, demonstrates the Standard Model origin of this $Delta I = 1/2$ rule enhancement.
The photon polarization in $D_{(s)} to K_1 (to Kpipi) gamma$ decays can be extracted from an up-down asymmetry in the $K pi pi$ system, along the lines of the method known to $B to K_1 (to Kpipi) gamma$ decays. Charm physics is advantageous as partne r decays exist: $D^+ to K_1^+ (to Kpipi) gamma$, which is standard model-like, and $D_s to K_1^+ (to Kpipi) gamma$, which is sensitive to physics beyond the standard model in $|Delta c| =|Delta u|=1$ transitions. The standard model predicts their photon polarizations to be equal up to U-spin breaking corrections, while new physics in the dipole operators can split them apart at order one level. We estimate the proportionality factor in the asymmetry multiplying the polarization parameter from axial vectors $K_1(1270)$ and $K_1(1400)$ to be sizable, up to the few ${cal{O}}(10)%$ range. The actual value of the hadronic factor matters for the experimental sensitivity, but is not needed as an input to perform the null test.
We present for the first time a model-independent anatomy of the ratio $varepsilon/varepsilon$ in the context of the $Delta S = 1$ effective theory with operators invariant under QCD and QED and in the context of the Standard Model Effective Field Th eory (SMEFT) with the operators invariant under the full SM gauge group. Our goal is to identify the new physics scenarios that are probed by this ratio and which could help to explain a possible deviation from the SM that is hinted by the data. To this end we derive a master formula for $varepsilon/varepsilon$, which can be applied to any theory beyond the Standard Model (BSM) in which the Wilson coefficients of all contributing operators have been calculated at the electroweak scale. The relevant hadronic matrix elements of BSM operators are from the Dual QCD approach and the SM ones from lattice QCD. Within SMEFT, the constraints from $K^0$ and $D^0$ mixing as well as electric dipole moments limit significantly potential new physics contributions to $varepsilon/varepsilon$. Correlations of $varepsilon/varepsilon$ with $Ktopi ubar u$ decays are briefly discussed. Building on our EFT analysis and the model-independent constraints, we discuss implications of a possible deviation from the SM in $varepsilon/varepsilon$ for model building, highlighting the role of the new scalar and tensor matrix elements in models with scalar mediators.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا